Walking beam furnace construction

ABSTRACT

THIS DISCLOSURE RELATES TO A WALKING BEAM FURNACE FOR HEATING BILLETS TO HIGH TEMPERATURE IN WHICH THE BILLETS ARE SUPPORTED AT THE SIDES OF THE WALKING BEAM BY SPACED, REMOVABLE REFRACTORY BLOCKS. METAL CAPS ARE PLACED ON THE CORNERS OF THE REFRACTORY BLOCKS TO REDUCE WEAR ON THE CORNERS AS A RESULT OF CONTINUED CONTACT WITH THE BILLETS DURING THEIR MOVEMENT THROUGH THE FURNACE. SLOPING SURFACES ARE FORMED BETWEEN THE REFRACTORY BLOCKS TO FACILITATE THE ENVELOPING OF THE BILLETS WITH A HIGH HEAT INTENSITY FLAME WHILE THE BILLETS ARE SUPPORTED BY THE REFRACTORY BLOCKS.

Sept. 20, 1971 c. B. GENTRY WALKING BEAM FURNACE CONSTRUCTION 3 Sheets-$heet 1 Filed Nov. 14, 1969 INVENTOR CHARLES H. GENTRY x x S O :3: 3@ 1: @N m 5 a ATTORNEYS Sept. 20, 1971 c. B. GENTRY 3,606,280

WALKING BEAM FURNACE CONSTRUCTION Filed Nov. 14. 1969 3 Sheets-Sheet 2 Sept, 2 1971 c. B. GENTRY WALKING BEAM FURNACE CONSTRUCTION 3 Sheets-Sheet 3 Filed Nov. 14. 1969 n4 no FIGS U ulll.

M w m United States Patent 3,606,280 WALKING BEAM FURNACE CONSTRUCTION Charles B. Gentry, Grand Rapids, Micl1., assignor to Granco Equipment, Inc., Grand Rapids, Mich. Filed Nov. 14, 1969, Ser. No. 876,666 Int. Cl. F27b 9/14 US. Cl. 263-6A 7 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to a walking beam furnace for heating billets to high temperatures in which the billets are supported at the sides of the walking beam by spaced, removable refractory blocks. Metal caps are placed on the corners of the refractory blocks to reduce wear on the corners as a result of continued contact with the billets during their movement through the furnace. Sloping surfaces are formed between the refractory blocks to facilitate the enveloping of the billets with a high heat intensity flame while the billets are supported by the refractory blocks.

DISCLOSURE This invention relates to a walking beam furnace. In one of its aspects it relates to a walking beam furnace for heating billets by direct flame impingement whereby the billet support means at the sides of the furnace comprise removable refractory blocks.

In the heating of billets by direct flame impingement, it is desirable for the flame to envelop the billets. This has been accomplished with the use of spaced, supporting rollers on which the billets move through the furnace. This has also been accomplished with the use of special conveyors which support the billets at spaced points.

The furnaces have been quite successful for heating low temperature alloys such as aluminum. For higher temperatures, such as copper alloys, the metal required for the supports becomes weak and has a short life.

I have now discovered a new and improved billet heating furnace for high temperature alloys in which a walking beam comprising refractory members is employed, and wherein spaced refractory supports along the sides of the walking beam support the billets so that the billets are substantially enveloped by the flame.

By various aspects of this invention one or more of the following, or other, objects can be obtained.

It is an object of this invention to provide a furnace for rapidly heating high temperature alloys to high temperatures.

It is another object of this invention to provide a walking beam furnace for heating billets in which the billets are substantially enveloped with a reducing portion of a flame.

It is yet another object of this invention to provide a walking beam furnace in which wear on the furnace parts is minimized.

It is yet another object of this invention to provide a walking beam furnace in which the parts subjected to the most wear are easily replaceable.

Other aspects, objects, and the several advantages of this invention are apparent to one skilled in the art from a study of this disclosure, the drawings, and the appended claims.

According to the invention there is provided a walking beam furnace construction comprising furnace walls formed of refractory material and defining a longitudinal furnace chamber with an opening at the bottom portion thereof. Billet support means are spaced along the longitudinal opening at opposite sides thereof. A walking beam is positioned within the longitudinal opening and ice means are provided to drive the walking beam through an orbital path whereby the top surface of the walking beam passes above and below the billet support means to move the billets through the furnace. The billet support means comprise removable refractory blocks, each of said blocks extending above and inwardly of the furnace walls so that the billets are supported entirely by said refractory glticks when the top surface of said walking beam is theree ow.

The invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a partial side elevational view in section illustrating a furnace according to the invention;

FIG. 2 is a front elevational view in section taken along lines 22 of FIG. 1;

FIG. 3 is a partial front elevational view in section taken along lines 33 of FIGv 1;

FIG. 4 is a partial sectional view seen along lines 44 of FIG. 2;

FIG. 5 is a partial sectional view along lines 55 of FIG. 4.

Referring now to the drawings, and to FIGS. 1 through 3 in particular, there is illustrated a furnace 12 for heating a plurality of cylindrical billets 10. The furnace has an entrance end 14 and an exit end (not shown). Side wall panels 18 and a top wall panel 20 encase the furnace. An exhaust manifold 22 and an exhaust conduit 24 have a fan 26 which draws exhaust gases through adjustable exhaust pipes 28 from the furnace.

The furnace is formed from a top refractory member 30 having vertical exhaust holes 32 which communicate with the exhaust pipes 28 for removing gases from the furnace. Bottom refractory members 34 form the bottom portion of the furnace and are spaced from each other to provide a longitudinal opening 36. A walking beam 38 is positioned for circular or orbital movement within the longitudinal opening 36. The walking beam 38 is formed from a plurality of refractory blocks 40 having a wide V-shaped upper surface, a cooled support member 42 and a support I beam 48. The cooled support 42 has water passages 44 and 46 through which water is circulated to provide a cooled barrier bet-ween the support I beam 48 and the refractory block 40. The refractory blocks 40 have a recess 41 at the bottom. A spline bar 52 fits within the recess 41 and positions the refractory block 40 on the support 42. Means (not shown) are provided at either end of the walking beam to resiliently compress the refractory blocks 40 to hold them in place.

Angle irons secure the cooling block 40 on the I beam 48.

A bottom heat seal for the furnace is formed by troughs 54, which are secured to the bottom of the furnace, and by sealing flanges 56, which depend from the top of the I beam 48 and extend into the trough 54. Water or sand or other suitable sealing material can be provided in the troughs to prevent air from entering the furnace through the longitudinal opening 36.

The walking beam is supported by an eccentric drive comprising an annular support member 58 which journals an eccentric hub 60 through bearings 62. The eccentric hub 60 is supported at the sides by side holder 64, upright supports 66 and horizontal hollow tubular beams 68. The outboard end 70 of the eccentric hub 60 has a sprocket wheel 72 fixed thereto. A chain 74 engages the sprocket 72 and a sprocket wheel 78 to drive the eccentric hubs 60. The sprocket wheel 78 is driven through a motor 84, a drive shaft 82 and gear box 80.

The furnace refractory sections 34 are supported by the I beams 68 and upright support beams 76.

The walking beam is biased upwardly by a gas cylinder 86. A box beam '88 having an upright flange pivotally supports the gas cylinder 86 through depending ears 92 and pin 94. The piston rod 96 from the gas cylinder 86 extends upwardly through an aperture in the support I beam 48 and pivotally engages the I beam 48 through collar 98, plates 100 and pin 102. A constanct gas pressure is supplied to cylinder '86 through an air supply manifold 104 and flexible conduit 106. The manifold 104 is formed from the tubular beams 68. A manifold (not shown) is provided between the beams to equalize the pressure in the manifolds 104. A vent 108 is provided at the upper portion of the gas cylinder to permit the upper part of the cylinder to breathe as the piston moves within the cylinder with the vertical movement of the walking beam 38.

A billet loading device is schematically illustrated in FIG. 1 at the entrance end 14 of the furnace. The loading device has rollers 11 which are journalled in a horizontal support 13. Vertical supports 15 are fixed to the horizontal support 13. The rollers can be powered by a motor (not shown) or a simple pusher mechanism (not shown) can be used to push the billets into the furnace when the walking beam is in its lowermost position. Rollers can be provided at the sides of the furnace adjacent the walking beam at the very front of the furnace to aid in moving the billet into the furnace.

Referring now to FIGS. 4 and 5, the bottom refractory members 34 are formed from a plurality of sections approximately two feet long extending the length of the furnace. Each section contains a plurality of spaced openings 110 which are juxtaposed to sections having sloping inner corners 112. Separate and removable pier blocks 114 fit into the openings 110 and extend out into the furnace above the sloping inner corners 112 for supporting the billets 10. Each pier block 114 has a rounded corner and a support corner cap 116 thereon. The support corner cap 115 is made out of a high temperature alloy metal and the pier blocks 114 are made out of a refractory material. The billets are supported by and contact the caps 116. The caps 116 are semicylindrical in shape, are hollow and contain a semicircular plate at one end only. The semicircular plate faces the entrance end of the furnace and the open end faces the exit end of the furnace. The caps 116 are thereby adapted to fit on the corners of block 114 within a wide range of tolerances for such corners. The caps 116 are maintained in the proper position on block 114 by the contact of the caps 116 with the billets as they move through the furnace. The billets will have a slight movement toward the exit end of the furnace as they are placed on the blocks 114 by the walking beam. By such movement, the caps 116 are subjected to a force toward the exit end of the furnace.

The furnace is fired by a plurality of burner tiles forming an upper row 117a having nozzles 118a and a lower row 1171: having nozzles 11817. The burners direct a flame into the center of the furnace to envelop the billets with a reducing portion of the flame. The upper row 117a is directly above the pier blocks and the lower row 117b is above the sloping corners 112. The flames from the lower row 1171) of burner tiles will extend down along the sloping corner 112 and envelop the bottom of the billets when the billets are heated on the pier blocks 114 and will pass beneath the billets when the billets are raised off the pier blocks. The flames from the upper row 117a will tend to pass over the tops of the billets regardless of whether the billets are resting on the pier blocks or are raised in the position shown.

As an alternate embodiment, the refractory blocks 40 can comprise juxtaposed sections of higher and lower refractory blocks to permit the flame to pass beneath portions of the billets when the billets are supported by the walking beam. The higher refractory blocks will support the billets and the flame will pass between the lower refractory blocks and the billets.

In operation, the furnace is opened and a billet 10 is moved into the furnace from the loading rollers 11 on to the side support members while the beam is at its lowermost position. As the walking beam is raised, the billet rests on the wide U-shaped'upper surface of the refractory blocks 40. All billets are generally in end to end contact on the walking beam refractory members 40 for maximum space utilization. The billets are moved through the furnace on the walking beam and are removed by a suitable billet retriever (not shown).

The billets are moved from the entrance end to the exit end of the furnace by the walking beam 38. The beam moves in an orbital motion in a vertical plane (as viewed in FIG. 1) with the top of the refractory blocks 40 rising above the top of the pier blocks 114 as the beam moves towards the exit end of the furnace. After the top of the refractory blocks 40 has fallen below the top of the pier blocks, the beam then moves back towards the front end of the furnace. In the drawings, the walking beam is shown in its uppermost position. When a billet reaches the very end of the furnace, its presence is sensed, and the walking beam is stopped, leaving the billet to rest on the pier blocks 114.

The billets are also supported by the pier blocks 114 during that time in which the beam 38 moves back towards the front end of the furnace. The billets are supported by the refractory blocks 40 as the beam 38 moves towards the exit end of the furnace. In this manner, the billets are moved from the entrance end of the furnace to the exit end thereof in incremental steps.

The billets are heated in the heating section of the furnace as they move therethrough by direct impingement of the flame from the burners on the billets. Preferably, the billets are enveloped by a reducing portion of the flame to minimize oxidation on the outer surface of the billets. This is accomplished by adjusting the velocity and mixture of the combustible fuel entering the burners. The products of combustion are exhausted from the furnace through the vertical exhaust holes 32, exhaust pipes 28, manifold 22 and exhaust conduit 24. The special furnace construction of alternating supports and sloping wall portions greatly facilitates the heating of the billets by direct flame impingement.

Movement of the beam 38 is caused by eccentric hub 60 which rotates by sprocket wheel 72 and chain 74. A plurality of such hub containing mechanisms are spaced along the length of the furnace. Each such mechanism is driven by motor 84 at a constant speed through drive shaft 82, gear box and chain 74. Thus, the hub 60' rotates at a constant speed, thereby moving the walking beam 38 at a constant rate.

The movement of the walking beam is aided and cushioned by the application of air pressure through cylinders 86 and piston rod 96. The cylinders are also disposed along the length of the furnace. Each cylinder is filled with a predetermined pressure from manifold 104. This air pressure is transmitted through the piston rod 96 to the beam 38. The air pressure in the cylinder can be adjusted to minimize the power requirements or current draw of the motor. This can be done manually or automatically through suitable instruments.

The air pressure assists the motor in raising the beam and in lifting the billets off the pier blocks. As the beam starts to move downwardly from its uppermost position, the air pressure continues to apply an upward force to the beam, thereby acting against the weight of the billets and the beam. In this manner, the reverse torque caused by the weight of the billets and the waking beam can be minimized. Further, the torque reversal on the motor due to the change from upward to downward motion of the walking beam is severely cushioned. The air pressure can be adjusted to substantially eliminate the torque reversal effect by adjusting the air pressure so that the force on the beam from the gas cylinders is equal to or greater than the weight of the beam. In such a case, the motor will be Working against the air pressure in the downward cycle.

The effect of the air cylinder is to minimize the force required for operating the walking beam and to decrease the wear on the motor drive and its associated moving parts. Therefore, smaller motors can be used to operate the walking beam and these smaller motors will have longer life.

The gas cylinders 86 have an open connection to the manifold 104. The pressure in the manifold remains substantially constant, and therefore the pressure in the gas cylinders remain substantially constant. The force from the gas cylinders is thus substantially constant but yieldable with the movement of the walking beam. The billets have a floating or cushioned ride on the walking beam with the use of the gas cylinders 86.

This floating ride of the walking beam avoids banging of the support parts due to torque reversal and permits more accurate control of the beam. The billets can be raised and lowered onto the supporting pier blocks much more gently to thereby minmize wear on these parts. Further, this floating action minimizes the surface scratches and defects in the billets as a result of the contact between the billets and their stationary supports. billets and their stationary supports.

The heated billets can be removed from the exit end of the furnace by any suitable device. A particularly suitable device is disclosed and claimed in my copending US. patent application Ser. No. 876,860, filed of even date herewith, entitled Walking Beam Furnace With Billet Removal Means.

The furnace of the invention finds particular utility in heating high copper alloys for extrusion wherein the required temperature is in the range of 2000 to 2200 F. At such temperatures most metals and their alloys have little or no strength and oxidize rapidly. Thus, conventional billet heating furnaces in which metal is used for structural parts within the furnace are not suitable. By the construction of the novel furnace according to the invention, refractory parts are used exclusively within the heating portions of the furnace for structural purposes. The structural metal beam parts are protected from heat by the refractory walls and by the water cooled portions of the beam. The cooling of the beam gives a high degree of dimensional stability to the support I beam 48. This dimensional stability is desirable in minimizing the stress on the refractory blocks 40 as the temperature within the furnace changes.

The furnace construction according to the invention also provides for rapid heating of the billets by the direct flame impingement method in which the flame substantially envelops the billets with a reducing portion of the flame. The pier blocks 114 are made from high temperature refractory material and therefore have good strength at the high heating temperatures. The areas of contact between the blocks and the billets are protected from chipping and abrasion by the metal caps 116. These caps need not have substantial structural strength at high temperatures since they are wholly supported by the refractory pier blocks. The construction also permits easy replacement of the pier blocks 114 without a complete rebuilding of the furnace. The pier blocks receive the most wear and would be the first parts to require replacement.

The single walking beam structure facilitates sealing the furnace from ambient air. At the high temperatures at which the furnace operates, significant amount of oxidation can take place on the billets if the furnace is not properly sealed. The illustrated heat and air seal between the side walls and the walking beam is just one such seal which can be provided in the furnace between the walking beam and the walls. Many other types of heat seals will be suggested to those skilled in the art.

The slow movement of the billets upwardly as well as horizontally facilitates more accurate temperature measurement of the billets. The temperature of the billets are usually sensed by fixed optical pyrometers which read only a small area of any given billet within the furnace. With the slow movement of the billets in their undulating motion, the pyrometer can take an average reading over a larger surface area than on a stationary billet. Erroneous errors due to surface irregularities are thereby minimized.

Whereas the invention has been described with reference to a furance having upper and lower rows of burners spaced along the sides, it is within the scope of the invention to employ only a single row of burners in a furnace. A single row of burners would be more appropriate in such a walking beam furnace in which smaller billets were to be heated.

Whereas the invention has been described with reference to a particular billet retriever or remover, other types of retrievers or removal devices are possible within the scope of the invention.

Reasonable variation and modification are possible within the scope of the foregoing disclosure and the drawings without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as folows:

1. A walking beam furnace construction comprising: furnace walls formed of refractory material and defining a longitudinal furnace chamber with a longitudinal opening at the bottom portion thereof;

billet support means spaced along said longitudinal passage at opposite sides thereof;

a walking beam in said opening;

means to drive said walking beam through an orbital path whereby the top surface of said walking beam passes above and below said billet support means to move said billets through said furnace;

the improvement comprising:

a plurality of lateral openings in said furnace walls spaced along said longitudinal furnace chamber;

said billet support means including a plurality of independent and removable refractory blocks spaced from each other and positioned within said furnace wall lateral openings, each of said blocks extending above and inwardly of said furnace walls so that said billets are supported entirely by said refractory blocks when said top surface of said walking beam is below said refractory blocks.

2. A walking beam furnace construction according to claim 1 wherein said refractory blocks are juxtaposed to inwardly and downwardly sloping wall portions.

3. A walking beam furnace construction according to claim 2 further comprising burners spaced along said furnace chamber in the side walls thereof, said burners comprising an upper row and a lower row of burners in each side wall, each burner in said lower row being positioned above said downwardly sloping wall portions and each burner in said upper row being positioned above said refractory blocks.

4. A walking beam furnace construction according to claim 1 wherein the upper inner corners of said refractory blocks are rounded.

5. A walking beam furnace construction according to claim 4 further comprising metal caps on said rounded corners of said refractory blocks.

6. A walking beam furnace construction according to claim 1 further comprising metal caps on the billet supporting corners of said refractory blocks.

7. A walking beam furnace construction comprising:

furnace walls formed of refractory material and defining a longitudinal furnace chamber with a longitudinal opening at the bottom portion thereof;

billet support means spaced along said longitudinal passage at opposite sides thereof;

a walking beam in said opening;

3,606,280 l a 8 u means to drive said walking beam through an orbital whereby flames emanating from said flame dipath whereby the top surface of said walking beam recting means can pass downwardly along said passes above and below said billet support means sloping wall portions and beneath billets supto move said billets through said furnace; ported on said refractory blocks.

means for directing flames inwardly of said furnace 5 walls; References Cited the improvement in said billet support means com- UNITED STATES PATENTS prising: v- 1 1 refractory blocks extending above and inwardly of 2,848,206 58 Kniveton 263--6A said furnace walls whereby said billets are sup- 10 3,4503% 6/1969 Wllde 263' 6A ported entirely by said refractory blocks when J said top surface of said walking beam is below FOREIGN PATENTS said refractory blocks, said refractory blocks 656,252 1/1963 Canada 2636A being spaced from each other and juxtaposed to inwardly and downwardly sloping wall portions, 15 CHAR-LES MYHRE, Pnmary EXamlllel' 

